6 homages of the Seiko Tuna compared side by side with the original. Prices run from about $129 to about $219 at official stores. The closest design is the Addiesdive MY-H5C, with a Resemblance Score of 49.
About the original
Seiko introduced the first Tuna, ref. 6159-7010, in 1975. It combined a titanium monocoque case with a special gasket so that helium could not enter the case, and it carried a screwed-on shroud around the bezel. Collectors call it the Grandfather Tuna, and the Tuna nickname has since spread to the shrouded divers that followed.
The Prospex SBBN047 (2020) is a current quartz Tuna: a lug-less one-piece case with a shroud, a 7C46 quartz movement, a black dial with large white indices and brushed hands in the 1975 style, and 1000 m water resistance on a black silicone strap.
The original
Seiko
Tuna
Reference SBBN047, prospex marinemaster professional 1000 m, black dial, black silicone strap
Addiesdive MY-H5CDive, 47.5 mm, 1.9 mm smaller than the original
Addiesdive AD2090Dive, 47.4 mm, 2 mm smaller than the original, 5 reviews read
Addiesdive AD2509Dive, 41 mm, 8.4 mm smaller than the original
Addiesdive AD2098Dive, 41 mm, 8.4 mm smaller than the original, 1 review read
Thorn T012 Titanium Shroud GMT DiverDive, 47 mm, 2.4 mm smaller than the original, 2 reviews read
Thorn T015 Black Titanium Shroud DiverDive, 47 mm, 2.4 mm smaller than the original